Vulcanization of plastic products



Patented May 11, 1938 PATENTS OFFICE VULOANIZATION F PLASTIC PRODUCTS 1 1 Claude H.- Alexander, Cuyahoga Falls, Ohio, as-

signor to The B. York, N.

F. Goodrich Company, New Y., a corporation of New York No Drawing. Application April 17, 1937, Serial No. 137,587

' 9 Claims. m1. 106-22) This invention relates to the vulcanization of plastic products, and has for its object the vulcanization of saturated or unsaturated polymeric plastics containing reactive halogen.

I have discovered that by heating a polymeric plastic containing reactive halogen in, the presence of an aldehyde-amine condensation product, the properties -01 the plastics undergo changes similar to the changes in the properties of rubber when it is vulcanized. Since the exact mechanism of the reaction is not understood except to the extent that hydrogen chloride is evolved during vulcanization, probably giving cross-linked polymeric molecules, I refer to it as vulcanization without binding myself toany theory as to the nature of the process. In general, the solubility and thermoplasticity of the plastics are decreased, the tensile strength ;is increased, and the elongation is often increased by this vulcanization process. The vulcanized products are usually harder, especially when a large amount of vulcanizing agent is used- The plastics which are vulcanizable by the method of this invention are saturated or unsat- 25 urated polymeric products containing reactive halogen. By the term reactive halogen I mean that the products contain halogen which is split ofl as a hydrogen halide when heatedwith the vulcanizing agents of this invention. Such plastics include polyvinyl halides, polyvinyl halogenated organic esters such as polyvinyl chloracetate, polymerized chloroprene (chloro-Z-butadb cue-1,3) which is commercially known as Neoprene, chlorinated rubber, and other polymeric halogen-containing compounds.

The vulcanizing agents are the condensation products of an aliphatic aldehyde and an arcmatic amine. The aliphatic aldehydes which may be used include formaldehyde, acetaldehyde, aldol, propionaldehyde, butyraldehyde, etc. 'Tihe aromatic amines include such typical compounds as aniline, ortho, meta, and para toluidine, para phenylene diamine, alpha and beta naphthylamine, etc. Several diflerent compounds may be obtained from the condensation of an aldehyde and an amine by varying the proportions of the reactants and'the reacting conditions.

'Though the composition of many of the condensation products which accomplish the vulcanization is unknown, it isv believed that they all .contain open-chain compounds. By the term "open-chain compounds" as used in the appended claims, I mean compounds in which the nitrogen atoms do not enter into a ring. Thus open- 55 chain compounds may contain benzene rings,

Ireaction resembles the vulcanization of naphthalene rings, etc., but according to my definition, such compounds as pyridine, pyrrole, and quinoline are not open-chain compounds. Byproducts of the condensation which are heterocyclic compounds containing a nuclear nitrogen 5' atom, such as the quinoline-type compounds, are not useful as vulcanizing agents. The condensations should be controlled, if possible, to inhibit the formation of these products. A most satisfactory vulcanizlng agent may be obtained by 10 condensing one moi. of aniline with an excess over three mols of butyraldehyde, distilling ofi unreacted raw materials, and extracting by-product quinoline derivatives with acid, to produce a compound which is believed to be l-phenyliminol6 2,4-diethyl-octadiene-2,4. The properties of the vulcanized product depend upon the temperature and length. of vulcanization and somewhat upon the quantity of v'ulcanizing agent used. Compositions contain- 30 ing 10% of a vulcanizing agent are usually stiller and harder than compositions containing from 2% to 5%. I usually prefer to use from .5% to 10% of vulcanizing agent, though. greater and less amounts may be used. The vulcanization rubber in that the best results are secured at an optimum cure, overcuring producing a decrease in tensile strength and elongation. 1

The action of the vulcanizing agent is often very rapid, .and unless carefully controlled, it may result in brittle products having little practical value. Light-colored plastics have a tendency to darken underthe influence of the liberated hydrogen halides. F'Br these reasons, I usually include in the composition a stabilizer which prevents the reaction from proceeding too rapidly and lessens or obviates the tendency to 1 darken. The silicates oif the alkali and alkaline earth metals and the alkaline earth oiddes are 40 all excellent stabilizers. They should be used in relatively. large quantities where long cures or service at highvtemperatures are contemplated, since the hydrogen halides which are liberated react with them to form metallic halides, thereby 5 diminishing their stabilizing effects. 1 It is well known that gamma polyvinyl chloride may be plasticized to form very useful, easily molded, rubbery compositions. These compositions soften at low temperatures, however, and are rarely useful above C. To illustrate the eflfect obtained by the vulcanization of my invention, I prepare a typical plasticiz'ed polyvinyl chloride composition containing polyvinyl chlor- 1 ide parts by weight and tricresyl phosphate 65 100 parts. To one portion I add 4,parts 01' 1- phenylimino-2,4-diethyhoctadiene-2A and calcium silicate 5 parts. I cure both compositions in a press for 20 minutes at 297 F. At the end of the cure, the vulcanized stock is tenacious and is easily separated from the hot mold, but the sample containing no vulcanizing agent is a viscous-molten mass and must be cooled before-it can be removed from the mold. -'When a small piece of each stockis placed on a tight mill-at 150 F., the unvulcanimd stock easily knits together into a sheet The vulcanized stock, being non-thermoplastic, crumbles into a flne powder. To make an unvulcanized stock of the same hardness as thevulcanized stock the proportion of plasticizer must be reduced from 100' parts to approximately '15 parts.

Clay, barytes, zinc oxide, wood flour, and other pigments and fillers commonly used in the rubher and plastics industries may also be included in the compositions. Carbon black .is an especially .useful pigment, for it often affects the vulcanization to greatly increase the strength of the compositions. The tensile strength 01' a com position containing polyvinyl chloride 100 by weight, tricresyl phosphate 10,!) parts,. 5 p arts of 1-phenylimino-2,4-diethyl-octadierie-2A, and magnesium oxide 5 parts is,twe11ty .per cent. greater after cure it 5 parts or carbon black are incorporated therein before chring.

This vulcanization may alsobe carried out .in solution. This is a. particularly I useful of preparing non-thermoplastic .protective coatings. Plasticized polyvinyl chloride containing a vulcanlzingzagent is dissolved in warm chlortoluene. Before vulcanization starts, the solution is painted or sprayed upon any desired surface. By heating sufliciently, the solvent evaporates and vulcanization occurs, thereby forming a. flexible, non-thermoplastic film having great resistance to oxidation and solvents.

In another experiment. I prepared tensile sheets of polychloroprene 100 parts; polychloro; prene-98-parts and magnesium oxide 2 parts; and polychloroprene 96 parts, 2- parts of l-phenylimino -2,4-diethyl-octadiene 2,4,- and magnesium oxide 2 parts. hftercuring for 15 minutesat'260 F., the polychloropreneand polychloroprene con taining magnesiumoxide were soft sticky masses on which it was impossible to determine the tensile strength. The vulcanized stock, however, had

-a tensile strength oi 1470 lbs. per sq. in. andan e1ongation of;815%.- A stock containing polychloroprene 9i! parts, 1 part 01. l phenylimino- 2,4 diethyIwctadiene ZA, and magnesium oxide 1 part gave the remarkably high. tensile of 2035 lbs. per sq. in.;--and elongation-of 1 005% afte1; cure. Other compounds such as the condensation products of para phenylene diamine and butyraldehyde, of aldol and alpha naphthylamine, and many other conjugated dienes and trienes formed by an aldehyde-amine condensation produce similar vulcanization reactions with polychloroprene, polyvinyl chloride, or any of the other plastics containing reactive halogen.

While I have herein disclosed specific embodiments of my invention, I do not limit myself wholly thereto, for it will be obvious to anyone skilled in the art that many'modific'ations including substituting equivalent materials and varying the amounts of materials used are within the spirit and scope or the invention defined in the" appended claims.

I claim: 1.. The methodwhich comprises heating a polyvinyl halide with a condensation product of an aliphatic aldehyde with an aromatic amine, which product. contains at least one open-chain com-- pound. I

' 2. The method which comprises heating plasticized polyvinyl chloride with a condensation product of butyraldehyde and aniline, which product contains at .least one open-chain com-- pound.

3. The method which comprises completely polymerized polyvinyl chloride. witha plasticizer and a small proportion of l-phenylimIno-2,4-diethyl-octadiene-2,4, and heating.

4. The method which comprises mixing commethod pletel'y polymerized polyvinyl chloridewith a plasticizer, a stabilizer, carbon black, and ;a small proportion of 1- -phenylimino-2,4-,diethyl-octadien'e-2,4, and heating.

5. A composition resulting from the heat reaction of polyvinyl chloride with a. condensation product '01 an aliphatic aldehyde and an aromatic 'amine, which product contains at least one openchain compound.

6. A composition resulting trom the heat reaction of plasticized polyvinyl chloride with a condensation product oibutyraldehyde and aniline, which product contains at-least one openchain compound. I

'7. A composition resulting from the heat reaction 02 plasticized'polyvinyl chloride with l-phenylimino-2,4-diethyl-octadiene 2A.

8. v'I hemethodwl ich comprises heating a polyvinyl halide. with a condensation product of butyraldehyde and para phenylene diamine, which product contains at least one open-chain compound. a

9. The method which comprises heating a poiy- 

